1. Technical Field
The present invention relates to quantitative airway analyses using high-resolution images, and more particularly, to quantitative airway analyses using high-resolution images to estimate abnormalities related to airway dimensions.
2. Discussion of the Related Art
There is a growing interest in quantitative airway analyses using high-resolution Computed Tomography (CT) images to estimate abnormalities related to airway dimensions, including measurement of airway dilation or peribronchial thickening. As an example, see B. L. Odry, A. P. Kiraly, C. L. Novak, D. P. Naidich, and J. F. Lerallut, “Automated airway evaluation system for multi-slice computed tomography using airway lumen diameter, airway wall thickness and broncho-arterial ratio,” SPIE Medical Imaging 2006, vol. 6143, February 2006 and A. P. Kiraly, J. M. Reinhardt, E. A. Hoffman, G. McLennan, and W. E. Higgins, “Virtual Bronchoscopy for Quantitative Airway Analysis,” SPIE Medical Imaging 2005: Physiology, Function, and Structure from Medical Images, A. Amini and A. Manduca, eds., SPIE Proceedings vol. 5746, February 2005. The analyses are best conducted on two-dimensional (2D) cross-sections perpendicular to the airways' long axis. These types of cross-sections are often unavailable to the radiologist or technician and, as a result, measurements are often performed only if the airway is aligned with the axial plane. Even in the case where only qualitative evaluation is performed (e.g., airway is normal/abnormal), a perpendicular 2D cross-section is still desired.
Some methods can automatically generate an appropriate cross-section using orientations supplied by a centerline from a bronchial tree model. In turn, the model is obtained from a manual, semi-automatic or fully automatic extraction of the bronchial tree. As an example, see A. P. Kiraly and W. E. Higgins, “Three-dimensional path planning for virtual bronchoscopy,” IEEE Trans. Med. Img., vol. 23, no. 11, pp. 1353-1364, November 2004 and A. P. Kiraly, W. E. Higgins, G. McLennan, E. A. Hoffman, and J. Reinhardt, “3D human airway segmentation methods for clinical virtual bronchoscopy,” Journal of Academic Radiology, vol. 9, no. 10, pp. 1153-1168, October 2002.
However, it is often the case that such segmentations of the bronchial tree are time-consuming (e.g., in the case of manual and semi-automatic) and/or do not reach distal airway branches. The result will generally be an inability to visualize and measure some branches of the airway tree. Although it may be possible to specify the orientation manually, it would add to the already strained workload of the radiologist/technician and create more user variability in measurements. Accordingly, there is a need for an automated method to obtain the orientation in cases where the tree model is not available.